Universal outlet for filter units

ABSTRACT

Filter device comprising a filter housing, a filter disposed in the filter housing, an inlet, and an opposed outlet spaced from the inlet, wherein the outlet comprises an extension from the housing, the extension extending longitudinally in the direction of fluid flow and comprising at least a first section having a minimum outer diameter and a second section downstream from the first section and having a terminal end having a maximum outer diameter, the maximum diameter of the second section terminal end being smaller than the minimum diameter of the first section.

BACKGROUND OF THE INVENTION

[0001] Filtration of solutions is generally desired to remove particlesin sample preparation applications, analytical techniques and prior toan instrumentation analysis, for example, or to sterilize a solution intissue culture applications. Depending upon the volumes that need to befiltered, different syringe driven filter sizes, identified by theirfilter diameter, are available. These include 4 mm, 13 mm and 25 mmsizes. The 4 mm syringe driven filters are typically recommended for thefiltration of volumes less than or equal to 1 ml.

[0002] Conventional syringe drive filters have male and female luertaper fittings designed to mechanically connect two medical devices suchas a syringe and a needle. As shown in FIG. 1, most conventional syringedriven filters have a female luer lock inlet and male luer slip outlet.The female luer lock inlet ensures that the filter is securely (butremovably) attached to the outlet of the syringe so as to preventleakage and loss of sample while filtration takes place. This isespecially critical when low sample volumes are being filtered. The lockis conventional and includes outer annular wings designed to beremovably engaged (by twisting) in corresponding thread-like ribs in theoutlet portion of the syringe. The internal diameter of the female lueris standardized, according to ANSI specifications, to receive acorresponding standardized male luer such as on a syringe. Thisstandardization ensures that the male and female portions will properlymate. As an alternative to the luer lock design, a friction fit (“luerslip”) can be used, especially in low-pressure applications.

[0003] Similarly, the male luer slip outlet on the syringe driven filterdevice allows, for example, a needle to be attached to the outlet of thefilter and facilitates a direct injection of a filtered sample into anHPLC (high pressure liquid chromatography) instrument, for autosamplervials or other receptacle for further analysis.

[0004] Another conventional syringe driven filter device is illustratedin FIG. 2. This device includes a narrowed outlet or “recorder taper”used in place of the male luer slip of the device of FIG. 1. Therecorder taper is narrower than the male luer slip, and thus does notfunction as a luer (i.e., it does not allow for a friction-fitengagement with a standardized female luer). However, the recorder taperfacilitates filtration into small receiving vessels such as HPLCautosampler vials, vial inserts and the wells of microtitre plates. Thesmaller outlet further minimizes the potential of the filtered samplebecoming lodged (“airlocked”) through capillary action in the top of thenarrow receiving vessel such as an autosampler insert, as the air caughtbeneath the sample cannot escape to allow the sample to flow to thebottom of the vessel. An additional feature of this design is a verysmall downstream (internal volume after the membrane) volume attributedto a smaller internal diameter in the outlet. This can be especiallyimportant with small sample volumes.

[0005] A still further conventional design is shown in FIG. 3. Thisdesign is a 4 mm syringe driven filter with a “tube tip” or “tubeoutlet”. A short tube is inserted into the outlet orifice of thestandard male luer slip design in order to facilitate the filtrationinto a small receiving vessel. However, this design suffers from thedrawback of having a larger downstream volume by virtue of the length ofthe tube tip, which is undesirable with small sample volumes.

[0006] It therefore would be desirable to provide a filter device suchas a syringe driven filter that includes all of the features ofconventional devices, but does not suffer from any of their drawbacks.

[0007] It further would be desirable to provide a filter device that hasmultiple outlet features so that a single device can serve multiplelaboratory filtration applications, thereby reducing the number ofspecialized filters the user needs to have on hand.

SUMMARY OF THE INVENTION

[0008] The problems of the prior art have been overcome by the presentinvention, which provides a filter device comprising a filter housing, afilter disposed in the filter housing, an inlet, and an opposed outletspaced from the inlet, wherein the outlet comprises an extension fromthe housing, the extension extending longitudinally in the direction offluid flow and comprising at least a first section having a minimumouter diameter and a second section downstream from the first sectionand having a terminal end having a maximum outer diameter, the maximumdiameter of the second section terminal end being smaller than theminimum diameter of the first section. In a preferred embodiment, thefilter device is syringe driven, the inlet is a female luer section, andthe first section of the outlet comprises a shortened male luer section.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a front view of a conventional syringe driven filterdevice having a female luer lock and a male luer slip;

[0010]FIG. 2 is a front view of a conventional syringe driven filterdevice having a female luer lock and a recorder taper outlet;

[0011]FIG. 3 is a front view of a conventional syringe driven filterdevice having a female luer lock and a tube outlet;

[0012]FIG. 4 is a perspective view of a syringe driven filter deviceaccording to one embodiment of the present invention;

[0013]FIG. 5 is a side view of the filter device of FIG. 4;

[0014]FIG. 6 is a cross-sectional view of the filter device of FIG. 4;

[0015]FIG. 7 is a side view of one embodiment of the present inventionshowing a syringe attached to the inlet of the filter device;

[0016]FIG. 8 is a side view of one embodiment of the present inventionshowing a pipette tip attached to the inlet of the filter device;

[0017]FIG. 9 is a side view of one embodiment of the present inventionshowing a pipette tip attached to the outlet of the filter device; and

[0018]FIG. 10 is a side view of another embodiment of the presentinvention showing a pipette tip attached to the outlet of the filterdevice.

DETAILED DESCRIPTION OF THE INVENTION

[0019] Turning now to FIGS. 4 and 5, there is shown a 4 mm syringe drivefilter unit 10 in accordance with one embodiment of the presentinvention. (Those skilled in the art will appreciate that the filterdevice of the present invention encompasses any device that utilizespressure differential across the filter to drive the liquidtherethrough, including syringes, pipettors and centrifuge- assistedapplications, and that the syringe driven devices illustrated anddiscussed are exemplary only.) The device 10 includes an inlet end 12and an outlet end 14 longitudinally spaced from the inlet end 12 in thedirection of fluid flow through the device. The inlet end 12 comprisesan aperture or opening 30 (FIG. 6) providing fluid communication intothe filter device housing. In a preferred embodiment of the presentinvention, the inlet end 12 comprises a female luer section designed inaccordance with conventional ANSI specifications. A centrally locatedbore 35 is provided to allow fluid communication between the device 10and another device containing the sample to be filtered that is to beattached to the female luer in a leakproof manner, such as a syringe 60(FIG. 7). It is preferred that the female luer include means toeffectuate a luer lock, such as outer annular protrusions 15 which areconfigured to screw into corresponding thread-like ribs in a male luerlock of the syringe 60 or the like. The luer lock prevents both axialand rotational movement of the filter device 10 with respect to theattached device, once engaged. Alternatively, a friction or slip fit isoften suitable, such as in connection with the terminal end of a pipettetip 65 as shown in FIG. 8.

[0020] Suitably located in the housing 20 of the filter unit 10 is afilter 40. The choice of filters will depend upon the application and isnot particularly limited; depth filters, microporous filters,ultrafiltration filters, adsorptive filters and any other filters orseparations media can be used. Preferably the filter 40 is secured inproximity to the base 21 of the housing 20 in a conventional manner,such as thermally, adhesively, chemically or mechanically such as withcompression. An underdrain structure 45 comprising one or more ports islocated beneath the filter 40, in the direction of fluid flow, tosupport the filter and to direct filtrate to flow into the internalaxial bore 28 and towards the outlet 14 of the device 10. Those skilledin the art will appreciate that the 4 mm version of the syringe drivenfilter device 10 is shown by way of example, and that smaller and largerdevices, such as 13 mm, 25 mm and 50 mm filters, are within the scope ofthe present invention. Although in such larger devices the housing 20configuration changes (e.g., can be disc shaped rather than cylindricalas in the 4 mm embodiment) in order to accommodate the larger filter,the inlet 12 portion and outlet 14 portion are the same.

[0021] Optionally formed in the outer surface of the housing 20 such asnear the base 21 are a plurality of nubs, grooves, ridges 23 or the likedesigned to assist the user in handling the filter unit 10.Alternatively, spaced projections, wings or surface textures could beused to provide the same function.

[0022] The outlet 14 portion of the device 10 comprises an extension 50extending longitudinally from the housing in the direction of fluidflow. The extension 50 comprises at least a first section 25 in fluidcommunication with the housing 20 through the filter and underdrain, thefirst section 25 having a certain minimum outside diameter. Although theoutside diameter of the first section 25 can vary along its length, theminimum outside diameter referred to herein is that portion of thesection 25 having the smallest outside diameter. The extension 50 alsocomprises a second section 26 in fluid communication with the firstsection 25 and extending in the longitudinally in the direction of fluidflow. In the embodiment shown, the second section 26 extends axiallydirectly from the first section 25 and is contiguous thereto. The secondsection 26 has a terminal end 47 having a maximum outside diameter thatis smaller than the minimum outside diameter of the first section 25.

[0023] In a preferred embodiment, the first section 25 is a male luerslip portion tapered and dimensioned in major diameter in accordancewith ANSI standards for a male luer, and has an internal axial bore thatis preferably centrally located. It is shorter (in the direction offluid flow) in length than conventional ANSI luers, in order toaccommodate the second section 26 without unnecessarily increasing thedownstream volume of the device. However, it cannot be too short or theintended luer connection to another device will not be secure. Thepresent inventor has determined that a luer length “a” (FIG. 5) of atleast about 2.7 mm, preferably about 3.7 mm, most preferably about 4.2mm, is sufficient to ensure that the connection does not fail duringtypical applications.

[0024] In the preferred embodiment shown, shoulder 27 is formed betweenfirst section 25 and second section 26 to define a steppedconfiguration. Like the first section 25, preferably the second section26 is tapered so that it narrows in diameter towards its free terminalend 47. This taper assists in the molding operation during manufacture.Preferably the second section 26 has a length of about 3.3 mm and thefree terminal end 47 thereof a diameter of about 3.16 mm. If the secondsection extends too far in the longitudinal axial direction, aninsufficient amount of the first section 25, when in the configurationof a male luer, may be available for engagement with a female luerfitting of a receptacle such as a needle, preventing a secure fit. Thefirst and second sections have communicating internal axial bores (shownas 28), preferably centrally located, the diameter of which can vary inaccordance with the application. The small outer diameter of theterminal end 47 of the second section 26 relative to the outer diameterof the first section 25 allows the tip of the device to be easilyinserted in a small receptacle, such as a standard HPLC vial or evensmaller HPLC vial insert, thereby ensuring that the sample beingtransported to that receptacle is not lost during transfer.

[0025] In alternative embodiments, the first section 25 is barbed so asto engage a suitable receptacle, or is configured to form a slip fitwith the inlet of a pipette tip 65, for example, as shown in FIG. 9.Similarly, the second section 26 could be barbed, or could be configuredto form a slip fit with the inlet of a pipette tip 65 as shown in FIG.10.

[0026] Since the filter units of the present invention are generallydisposable, they are preferably constructed of an inexpensivethermoplastic material such as a polyolefin, preferably polyethylene orpolypropylene. Those skilled in the art will appreciate that othermaterials of construction are suitable, such as stainless steel, wherethe economics so allow. A conventional molding operation can be used toform the units, which are preferably one integral piece.

[0027] Those skilled in the art will appreciate that the foregoingembodiments utilize generally cylindrical configurations, but that othershapes are within the scope of the present invention. Thus, the inletand/or the first and/or second sections could have polygonalcross-section, in which case the limitations discussed above withrespect to the dimensions of the outside diameters would instead applyto the outside perimeters.

What is claimed is:
 1. A filter unit for filtering a sample, comprising a housing for a filter having an inlet, an outlet spaced from said inlet, and a fluid passageway extending therethrough, said outlet comprising an extension extending longitudinally from said housing in the direction of fluid flow, said extension comprising at least a first section having a minimum outer diameter, and a second section downstream from said first section in the direction of fluid flow and having a terminal end having a maximum outer diameter, said maximum outer diameter of said terminal end being smaller than said minimum outer diameter of said first section.
 2. The filter unit of claim 1 , wherein said housing has a filter having a diameter selected from the group consisting of 4 mm, 13 mm, 25 mm and 50 mm.
 3. The filter unit of claim 1 , wherein said inlet comprises a female luer section.
 4. The filter unit of claim 1 , wherein said first section of said extension comprises a male luer section.
 5. The filter unit of claim 1 , wherein said first section of said extension is barbed.
 6. The filter unit of claim 1 , wherein said sample to be filtered is housed in a pipette having a terminal pipette tip, and wherein said inlet is configured to form a slip fit with said terminal pipette tip.
 7. The filter unit of claim 1 , wherein filtrate resulting from filtration of said sample is expelled out said outlet into a container comprising a pipette having a pipette inlet, and wherein said first section of said outlet is configured to form a slip fit with said pipette inlet.
 8. The filter unit of claim 1 , wherein filtrate resulting from filtration of said sample is expelled out said outlet into a container comprising a pipette having a pipette inlet, and wherein said second section of said outlet is configured to form a slip fit with said pipette inlet.
 9. A filtration device, comprising a housing having filter means supported therein, a fluid inlet to said housing, and a fluid outlet from said housing; said fluid outlet comprising a male luer section having a first axial bore in fluid communication with said housing and having a minimum outside diameter, and a tip portion extending axially from said male luer section, said tip portion having a second axial bore in fluid communication with said first axial bore, said tip portion having an outside diameter smaller than said minimum outside diameter of said male luer section.
 10. The filtration device of claim 9 , wherein said fluid inlet comprises a female luer section.
 11. A method of filtering a sample, comprising: providing a container for said sample, said container comprising a first male luer section; providing a filter device comprising a housing having a filter, an inlet, an outlet spaced from said inlet, and a fluid passageway extending therethrough, said inlet comprising a female luer section adapted to be removably secured to said first male luer section of said container in a leakproof manner, said outlet comprising a second male luer section having a minimum outside diameter and a tip portion extending axially from said second male luer section and having a terminal end, said terminal end of said tip portion being smaller in outside diameter than said minimum outside diameter of said second male luer section; providing a receptacle for filtrate; placing said terminal end of said tip portion in said receptacle; and causing said sample to flow from said container into said housing so as to be filtered by said filter and form a filtrate, said filtrate flowing through said second male luer section and said tip portion into said receptacle.
 12. The method of claim 11 , wherein said container is a syringe.
 13. A filter unit for filtering a sample, comprising a housing for a filter having an inlet, an outlet spaced from said inlet, and a fluid passageway extending therethrough, said outlet comprising an extension extending longitudinally from said housing in the direction of fluid flow, said extension comprising at least a first section having a minimum outer perimeter, and a second section downstream from said first section in the direction of fluid flow and having a terminal end having a maximum outer perimeter, said maximum outer perimeter of said terminal end being smaller than said minimum outer perimeter of said first section. 